feat(profile): default avatars via DiceBear "thumbs" (CC0), drop boring_avatars

Replace the flutter_boring_avatars fallback with a friendly DiceBear
"thumbs" face, generated offline (dicebear_core) and deterministically
from the pubkey, rendered as SVG (flutter_svg). The thumbs style is
CC0 1.0 (public domain) — no attribution, AGPL-clean — unlike Multiavatar
whose custom licence restricts use. Style parsed once and per-pubkey SVG
memoized; the CC0 <metadata> block is stripped to keep flutter_svg quiet.

apps/app_seeds/lib/ui/avatar.dart

@@ -6,7 +6,7 @@ import 'seed_glyph.dart';
 ///    media server, like offer photos);
 ///  - `tane:seed:<name>` — one of our own seed illustrations (for people who'd
 ///    rather not put a real photo — pseudonymity stays the default);
-///  - empty — a pattern avatar generated deterministically from the pubkey.
+///  - empty — a DiceBear "thumbs" face generated deterministically from the pubkey.
 const avatarGlyphPrefix = 'tane:seed:';
 
 /// The seed illustrations offered as ready-made avatars. Names are the stable

apps/app_seeds/lib/ui/peer_avatar.dart

@@ -1,27 +1,18 @@
+import 'package:dicebear_core/dicebear_core.dart' show Avatar, Style;
+import 'package:dicebear_styles/thumbs.dart';
 import 'package:flutter/material.dart';
-import 'package:flutter_boring_avatars/flutter_boring_avatars.dart';
+import 'package:flutter_svg/flutter_svg.dart';
 
 import '../services/offer_thumbnail.dart' show decodeDataUri;
 import '../services/profile_cache.dart';
 import 'avatar.dart';
 import 'seed_glyph.dart';
-import 'theme.dart';
-
-/// Palette for the generated default avatars — earthy seed-and-leaf tones so
-/// the fallback art sits inside the app's palette rather than fighting it.
-const _generatedAvatarPalette = BoringAvatarPalette([
-  seedGreen,
-  seedRating, // warm amber
-  Color(0xFFB5541F), // terracotta pot
-  Color(0xFF6B4F2A), // seed-coat brown
-  Color(0xFFD3E8C8), // pale leaf
-]);
 
 /// A small round avatar for a person. When they've set an avatar ([picture] — a
 /// `data:` photo thumbnail or a `tane:seed:<glyph>` illustration) it's shown;
-/// otherwise it falls back to a generated pattern drawn deterministically from
-/// their [pubkey] (boring-avatars "beam"). Same pubkey → same picture on every
-/// device, so a person stays visually recognizable without sharing anything.
+/// otherwise it falls back to a [GeneratedAvatar] drawn deterministically from
+/// their [pubkey]. Same pubkey → same picture on every device, so a person
+/// stays visually recognizable without sharing anything.
 class PeerAvatar extends StatelessWidget {
   const PeerAvatar({
     required this.pubkey,
@@ -34,7 +25,7 @@ class PeerAvatar extends StatelessWidget {
   final String pubkey;
   final String? name;
 
-  /// The person's chosen avatar value; null/empty → the coloured-initial disc.
+  /// The person's chosen avatar value; null/empty → the [GeneratedAvatar].
   final String? picture;
   final double radius;
 
@@ -58,16 +49,52 @@ class PeerAvatar extends StatelessWidget {
       }
     }
 
+    return GeneratedAvatar(pubkey: pubkey, name: name, radius: radius);
+  }
+}
+
+/// The `thumbs` DiceBear style, parsed once — [Style.parse] validates the style
+/// definition against its schema, which is not free to repeat per build.
+final _thumbsStyle = Style.parse(thumbs);
+
+/// Rendered-SVG memo keyed by pubkey, so a person's avatar is generated once and
+/// reused across every rebuild and list row rather than re-rendered each time.
+final _svgCache = <String, String>{};
+
+/// Strips the `<metadata>` block (the style's CC0 licence notice) that
+/// flutter_svg cannot parse and logs a warning for; CC0 requires no attribution
+/// in the rendered image, and the licence still ships with the package source.
+final _metadataElement = RegExp(r'<metadata\b[^>]*>.*?</metadata>', dotAll: true);
+
+String _renderThumbs(String pubkey) =>
+    Avatar(_thumbsStyle, {'seed': pubkey}).svg.replaceAll(_metadataElement, '');
+
+/// The deterministic default avatar for a person with no chosen [picture]: a
+/// friendly DiceBear "thumbs" face (CC0) seeded from their [pubkey], so the same
+/// key yields the same face on every device with nothing shared. Rendered as an
+/// SVG (no network, no assets). Exposes [pubkey] so call sites/tests can find it.
+class GeneratedAvatar extends StatelessWidget {
+  const GeneratedAvatar({
+    required this.pubkey,
+    this.name,
+    this.radius = 14,
+    super.key,
+  });
+
+  final String pubkey;
+  final String? name;
+  final double radius;
+
+  @override
+  Widget build(BuildContext context) {
+    final svg = _svgCache[pubkey] ??= _renderThumbs(pubkey);
     return Semantics(
       label: name,
       image: true,
-      child: SizedBox.square(
-        dimension: radius * 2,
-        child: BoringAvatar(
-          name: pubkey,
-          type: BoringAvatarType.beam,
-          palette: _generatedAvatarPalette,
-          shape: const OvalBorder(),
+      child: ClipOval(
+        child: SizedBox.square(
+          dimension: radius * 2,
+          child: SvgPicture.string(svg, fit: BoxFit.cover),
         ),
       ),
     );

apps/app_seeds/pubspec.yaml

@@ -78,7 +78,9 @@ dependencies:
   # while the app is foregrounded. Mobile/Linux/macOS only; a no-op on web and
   # Windows. Foreground-only by design — background/push is a later concern.
   flutter_local_notifications: ^18.0.1
-  flutter_boring_avatars: ^2.1.0
+  dicebear_core: ^10.3.0
+  dicebear_styles: ^10.2.0
+  flutter_svg: ^2.3.0
 
 dev_dependencies:
   flutter_test:

apps/app_seeds/test/ui/chat_message_list_test.dart

@@ -3,7 +3,6 @@ import 'dart:async';
 import 'package:commons_core/commons_core.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_bloc/flutter_bloc.dart';
-import 'package:flutter_boring_avatars/flutter_boring_avatars.dart';
 import 'package:flutter_localizations/flutter_localizations.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:tane/domain/chat_timeline.dart';
@@ -129,10 +128,10 @@ void main() {
     // so you can tell who said what at a glance.
     expect(find.byType(PeerAvatar), findsNWidgets(2));
     final generated = tester
-        .widgetList<BoringAvatar>(find.byType(BoringAvatar))
+        .widgetList<GeneratedAvatar>(find.byType(GeneratedAvatar))
         .toList();
     expect(generated, hasLength(2));
-    expect(generated.first.name, isNot(generated.last.name));
+    expect(generated.first.pubkey, isNot(generated.last.pubkey));
   });
 
   testWidgets('a new message lands in view at the bottom, not below the fold', (

apps/app_seeds/test/ui/peer_avatar_test.dart

@@ -1,5 +1,4 @@
 import 'package:flutter/material.dart';
-import 'package:flutter_boring_avatars/flutter_boring_avatars.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:tane/services/profile_cache.dart';
 import 'package:tane/ui/avatar.dart';
@@ -38,18 +37,19 @@ void main() {
       home: Scaffold(body: Center(child: child)),
     );
 
-    testWidgets('falls back to a generated pattern keyed by pubkey', (
+    testWidgets('falls back to a generated avatar keyed by pubkey', (
       tester,
     ) async {
       await tester.pumpWidget(host(PeerAvatar(pubkey: 'aa', name: 'rosa')));
-      final generated = tester.widget<BoringAvatar>(find.byType(BoringAvatar));
-      expect(generated.name, 'aa'); // pubkey, not name → stable across renames
+      final generated =
+          tester.widget<GeneratedAvatar>(find.byType(GeneratedAvatar));
+      expect(generated.pubkey, 'aa'); // pubkey, not name → stable across renames
       expect(find.byType(Text), findsNothing);
     });
 
     testWidgets('generates it even when the name is unknown', (tester) async {
       await tester.pumpWidget(host(const PeerAvatar(pubkey: 'aa')));
-      expect(find.byType(BoringAvatar), findsOneWidget);
+      expect(find.byType(GeneratedAvatar), findsOneWidget);
     });
 
     testWidgets('renders a seed illustration when the avatar is a token', (
@@ -76,19 +76,19 @@ void main() {
       expect(find.byType(SeedGlyph), findsOneWidget);
     });
 
-    testWidgets('falls back to the generated pattern when nothing is cached', (
+    testWidgets('falls back to the generated avatar when nothing is cached', (
       tester,
     ) async {
       final cache = ProfileCache(InMemorySecretStore());
       await tester.pumpWidget(host(
           CachedAvatar(pubkey: 'peer2', name: 'Bea', cache: cache)));
       await tester.pumpAndSettle();
-      expect(find.byType(BoringAvatar), findsOneWidget);
+      expect(find.byType(GeneratedAvatar), findsOneWidget);
     });
 
-    testWidgets('no cache → the generated pattern', (tester) async {
+    testWidgets('no cache → the generated avatar', (tester) async {
       await tester.pumpWidget(host(const CachedAvatar(pubkey: 'x', name: 'Bea')));
-      expect(find.byType(BoringAvatar), findsOneWidget);
+      expect(find.byType(GeneratedAvatar), findsOneWidget);
     });
   });
 }